The present invention relates to a parallel distributed sample scrambling and descrambling system.
A distributed sample scrambling (DSS) system suitable for scrambling the binary data consisting of fixed-sized packet stream scrambles and descrambles the binary data in the same way as that used in a Frame Synchronous Scrambling (FSS) system.
However, to achieve the effective scrambling in the DSS system, a method of synchronizing the state of the scrambler to the state of the descrambler is preferably different from that used in FSS system.
The synchronization in the DSS system is achieved by taking a sample representing the state of the scrambler, transmitting it to the descrambler over allocated time slots in every packet, comparing it to a sample generated from descrambler, and then if two samples are different from each other, correcting the state of descrambler so that the state of descrambler is identical to the state of scrambler.
According to recommendation by CC ITT, such DSS system is used for scrambling ATM (Asynchronous Transfer Mode) cell stream in the cell-based physical layer in BISDN (Broadband Integrated Services Digital Network).
The transmission rates in DSS system are multiple of 155.520 Mbps in the BISDN and the rates of 155,520 Mbps, 622.080 Mbps or 2488.320 Mbps are of special interests.
The scrambling and descrambling rates in the DSS system are identical to the corresponding transmission rates, i.e. 155.520 Mbps, 622.080 Mbps or 2488.320 Mbps. In achieving the scrambling at such high processing rates, it is disadvantageous that high speed elements are required, the production cost is increased and the power consumption is increased. Furthermore, in the case of high speed transmission of Gbps grade, the scrambling at transmission rates may be impossible.
Therefore, it is an object of the invention to provide a parallel distributed sample scrambling system for fixed-sized packet transmission which can scramble the binary data at lower rates than the transmission rates.
It is other object of the invention to provide a parallel distributed sample descrambling system for fixed-sized packet transmission which can descramble the binary data at lower rates than transmission rates.
To achieve these objects, the parallel distributed scrambling system according to the invention comprises: a parallel shift register generator for generating parallel sequences for parallel scrambling, said generator including a plurality of shift registers and a plurality of modulo-2 adders, a sampling means for generating samples from said parallel shift register generator depending on transmission channel slots available for sample conveyance, a parallel scrambling means for performing parallel scrambling function by modulo-2 adding the parallel sequences from said parallel shift register generator to parallel input data sequences, and a multiplexing means for multiplexing the scrambled data sequences from said parallel scrambling means. Also, a parallel distributed sample descrambling system for fixed-sized packet transmission according to the invention comprises: a demultiplexing means for demultiplexing the multiplexed scrambled data sequences, a parallel shift register generator for generating parallel sequences for parallel descrambling, said generator including a plurality of shift registers and a plurality of modulo-2 adders, a sampling means for generating samples from said parallel shift register generator depending on transmission channel slots available sample conveyance, a comparing means, connected to the sampling means, for comparing the samples transmitted from the scrambler with the samples generated by said sampling means, a correction means, connected to the comparing means, for performing correction for samples at each correction time according to the comparison result for said comparing means, and a parallel descrambling means for performing parallel descrambling of the scrambled data sequences by modulo-2 adding the parallel sequences from said parallel shift register generator to the scrambled data sequences from said demultiplexing means.